Lead for aircraft propeller electrical deicer system

ABSTRACT

A flexible, compact lead containing current-conducting wires extends within the spinner housing from the propeller assembly to a propeller blade unit which is relatively rotatable to adjust the pitch of the blade. The wires are encased in a sleeve having enlarged ends for secure clamping to the propeller assembly and to a clamping member on the propeller blade unit. The wear in this part of the system which receives the greatest stress and twisting is reduced by the lead construction and when replacement is necessary this can be done quickly without requiring replacement of the propeller deicer boot.

ited States Patent Nelson [54] LEAD FOR AIRCRAFT PROPELLER ELECTRICAL DEICER SYSTEM [72] Inventor: Grover 0. Nelson, Akron, Ohio [73] Assignee:' The B. F. Goodrich Company, New York,

[22] Filed: Aug. 20, 1970 [211 App]. No.: 65,519

[52] 11.8. CI ..219/20l, 219/202, 219/528, 339/1 R [51] Int. Cl. ..H05b 1/00 [58] Field of Search ..219/200-202, 527-529, 219/535; 339/1 R, 5 M, 5 R; 174/74 A, 74 R, 86

[56] References Cited UNITED STATES PATENTS 2,743,890 5/1956 La Rue ..2l9/202 X Feb. 22, 1972 2/1970 Fleury et al...

3,496,331 ..2l9/20l 2,757,273 7/1956 Taylor ....2l9/528 X 2,690,890 10/1954 Weeks et al.. ....2l9/202 X 2,797,761 7/1957 Barish et a1 ..339/5 M Primary Examiner-C. L. Albritton Anorney-John D. Haney and Frederick K. Lacher [57] ABSTRACT A flexible, compact lead containing current-conducting wires 'extends within the spinner housing from the propeller assembly to a propeller blade unit which is relatively rotatable to adjust the pitch of the blade. The wires are encased in a sleeve having enlarged ends for secure clamping to the propeller assembly and to a clamping member on the propeller blade unit. The wear in this part of the system which receives the greatest stress and twisting is reduced by the lead construction and when replacement is necessary this can be done quickly without requiring replacement of the propeller deicer boot.

9 Claims, 5 Drawing Figures LEAD FOR AIRCRAFT PROPELLER ELECTRICAL DEICER SYSTEM BACKGROUND OF THE INVENTION This invention relates to propeller deicing systems and espe-' cially to electrically heated deicers which are bonded to the propeller blades. These deicers contain electrical resistance heaters which are connected to a power source on the main body of the aircraft through a slipring mounted on the propeller assembly and brushes mounted on the aircraft.

Heretofore, the deicer boot containing the resistance heaters has been made with a strap extending towards the hub of the propeller where it has been clamped to the hub of the propeller as it enters the spinner housing. The strap has then been looped inside the spinner housing to provide slack for accommodating the propeller pitch adjustments and the currentconducting wires in the strap have been secured to terminals connected to the three sliprings mounted on the propeller as sembly.

This lead strap had a flat belt-type configuration because it was designed for fabrication with the deicer boot and mounting on the propeller surface. Accordingly, the section of the strap which was inside the spinner housing had limited flexibility and did not readily conform to the twisting and centrifugal forces which were exerted upon the strap during operation of the propeller. It has been found, therefore, that failure occurred in this strap portion before other portions of the deicer systems were worn out.

When the deicer strap-connecting portion needed to be replaced, the entire deicer boot had to be removed from the propeller blade and a new deicer boot installed. Not only was this costly but it also consumed valuable time to properly remove the boot from the propeller and then apply a new deicer to the propeller. Of course, during this time the aircraft could not fly. Another difficulty with the deicer strap used in the past was that in the configuration of a belt, it consumed considerable space within the spinner housing where space is at a premium because of the other mechanism therein and the aerodynamic limitations.

SUMMARY OF THE INVENTION The propeller deicing system of this invention provides for a detachable, flexible lead between the end of the lead strap where it enters the spinner housing and the propeller assembly where the power is received from the slipring. The detachable lead is of a construction which is highly flexible and can adjust to the different positions it is thrust into during rotation of the propeller when the centrifugal forces exerted on this lead reach very high magnitudes. The construction of the lead is such that it accommodates the twisting action which occurs when the propeller blade is adjusted to obtain the proper pitch for different operating conditions of the aircraft. This adjustment of the propeller blade may be as much as 120.

The radially inner end of the lead strap is clamped in place against the propeller hub by a clamping member which contains a portion for supporting the terminals around which the wires from the strap are connected and the wires from the detachable lead may be connected. This clamping member also serves as a support for a cable clamp which securely holds the end of the detachable lead in position. To further secure the detachable lead, a sleeve which encases the wires has enlarged end portions to prevent the ends from slipping out of the clamps.

The wires are wrapped in fabric and an insulating material encased in a sleeve which provides a lead that is not only flexible but withstands the severe twisting and turning forces exerted upon the lead during operation of the propeller. The lead has a round cross section and therefore takes up a minimum of space within the spinner housing.

With this construction, a flexible lead is provided in the area of the system which undergoes the greatest wear and stress during operation of the propeller. Because of the construction of the lead it requires far less maintenance than the prior construction where an extension of the lead strap of the deicer was used. Furthermore, when this lead needs repair or replacement, it may be done quickly and easily at a substantial savings in cost and time over the prior practice of removing the complete deicer including the boot and the lead strap and replacing it with a complete new assembly.

The accompanying drawings show one preferred form of a detachable lead for a propeller deicer system made in accordance with and embodying this invention and which is representative of how this invention may be practiced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary view of a three-blade propeller and engine nacelle of an aircraft.

FIG. 2 is an enlarged sectional view of a portion of the propeller assembly shown in FIG. 1 with parts being broken away and shown schematically in dot-dash lines.

FIG. 3 is a sectional view taken along the plane of line 33 of FIG. 2 showing the lead strap hub clamp of the invention, parts being broken away.

FIG. 4 is an exploded sectional view taken along the plane of line 44 of FIG. 3 with parts being broken away.

FIG. 5 is a longitudinal section of the lead showing the enlarged end for clamping and the construction of the insulated wires.

DETAILED DESCRIPTION Referring to FIG. 1, a three-blade propeller assembly 10 is shown mounted on a propeller shaft 11 which extends from an engine nacelle 12 of an aircraft which may be a singlepropeller or a multiple-propeller aircraft. The propeller assembly 10 has three propeller blades 13 which may be connected to the propeller shaft 11 by suitable mechanism well known in the art for changing the pitch of the propeller blades. A spinner housing 14 encases the pitch controlling mechanism for the propeller blades 13 and, as shown in FIG. 2, may be mounted on a spinner bulkhead l5.

Deicer boots 16 are mounted on the propeller blades 13 at the leading radially inner edge where ice tends to accumulate. Each boot 16 contains resistance-type electric heaters and because of the power required, there are usually two heaters in each boot, an inner and an outer heater, which are alternately activated during flight to conserve the power required to operate the deicers.

Each resistance heater in the boot is connected through a lead strap 17 to a source of power and to a ground connection and therefore each strap for each boot contains three conducting wires 18.

Each of the propeller blades 13 is part of a propeller blade unit 19 including a hub member (not shown) and other mechanism for holding the propeller in the propeller assembly 10 and turning it to adjust the pitch of the propeller. A clamping member such as bracket 22 is fastened to the propeller unit 19 as by screws 23 shown in FIGS. 2 and 3. The bracket 22 has 'an opening 24 at the radially inner edge through which the lead strap 17 may pass and be clamped by a bracket clamping portion 25 against the propeller unit 19 as shown more clearly in FIGS. 3 and 4. The bracket 22 has an outwardly extending connecting portion or flange 26 on which terminals 27, 28 and 29 are mounted for receiving conducting wires 18 and fastening the ends securely thereto.

A slipring assembly 32 is mounted as by bolts 33 and nuts 34 to the propeller assembly 10 at a position where three sliprings 35, 36 and 37 may be engaged by brushes mounted in a brush block (not shown) on the engine nacelle 12 and leading to a ground and the power source through a control assembly (not shown) for switching the power from one line to the other. The sliprings 35, 36 and 37 are connected to a terminal block 38 mounted on the spinner bulkhead 15 by connecting wires 39, 40 and 41.

A tubular support such as conduit 42 for connecting wires 39, 40 and 41 is held in position by angle bracket 43 mounted on the slipring assembly 32 as by bolt 48 and nut 49 and by angle bracket 50 mounted on the spinner bulkhead l and held by bolt 51 and nut 52 connected to the terminal block 38.

A detachable lead 53 is disposed between the terminal block 38'and terminals 27, 28 and 29 and has three insulated wires 57, 58 and 59 which are connected to the terminal block at one end and to the terminals at the other end. These insulated wires 57, 58 and 59 form a center core of lead 53 as shown in FIG. 5 surrounded by a sleeve member 63 of heat shrinkable material which is assembled and heated to shrink around an O-ring 64 of resilient rubberlike material surrounding the insulated wires at the ends of the lead to provide enlarged ends 65 and 66. The lead 53 is held securely to the spinner bulkhead 15 of the propeller assembly by suitable means such as a cable clamp 67 secured to the bulkhead by screw and nut assembly 68 and clamps the lead next to the enlarged end 65. The other end of the lead 53 is held securely by suitable clamping means such as cable clamp 69 fastened to the flange 26 by a suitable screw and nut assembly 70 and clamps the lead next to the enlarged end 66.

With reference to FIG. 5, a more detailed cross-sectionalview of the detachable lead 53 is shown. Each of the insulated wires 57, 58 and 59 has an inner core of conducting material such as copper and preferably this is made up of many strands 73 with approximately 105 strands in each wire in the embodi-.

ment shown. These strands 73 are wrapped in a fabric layer 74 and covered with an insulating layer 75 of nonconducting plastic material with the wire then being covered by another fabric layer 76. These three wires 57, 58 and 59 are then covered by the sleeve 63 of heat shrinkable material which is in turn covered by a protective covering 77 of wear-resistant material which terminates short of the ends 65 and 66. The length of the detachable lead 53 is at least as great as the maximum distance between the cable clamp 67 and cable clamp 69 when the propeller blade unit 19 is turned to obtain the desired pitch.

in operation, the propeller assembly 10 rotates at a high rate of speed creating a centrifugal force thrusting the detachable lead 53 radially outward against the spinner bulkhead l5 and other parts of the propeller assembly. Because of the construction described above, the detachable lead 53 is very flexible and will bend and twist-without creating serious wear of the wires 57, 58 and 59 and other components of the lead. The lead 53 is held firmly in position by cable clamps 67 and 69 with the enlarged ends 65 and 66 of'the lead preventing sliding movement of the lead out of the cable clamps and therefore preventing undue strain on the ends of the wires which are fastened to the terminal block 38 and terminals 27, 28 and 29. Because of the flexible nature ofthe detachable lead 53 and its round cross section, it conforms to the available space within the spinner housing 14. 7

In the maintenance of this propeller assembly 10 and the deicer system, the greatest wear will occur in the area of the detachable lead 53 and this is the part which will probably wear out first. When this occurs, it is a simple matter to remove the detachable lead 53 simply by loosening the screw and nut assemblies 68 and 70 of the cable clamps 67 and 69 and then disconnecting the ends of the wires 57, 58 and 59 from the terminal block 38 and from the terminals 27, 28 and 29. A new detachable lead 53 may then be inserted in the cable clamps 67 and 69 with the enlarged ends 65 and 66 extending therethrough and the screw and nut assemblies 68 and 70 tightened around the lead 53. The ends of the wires may then be fastened in the terminal block 38 and to the terminals 27, 28 and 29. With this construction it is no longer necessary to remove the deicer boot 16 and lead strap 17 from the propeller l3 and install a new unit.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim: 1. An aircraft propeller electric deicer system comprising a boot containing a resistance-type electric heater mounted on a propeller blade and a lead strap containing lead strap wires extending from said boot radially inward to a clamping member mounted on a propeller blade unit having pitch adjusting rotation relative to a propeller assembly, said clamping member being fastened to said propeller blade unit and having terminals for connecting the lead strap wires with wires of a detachable lead extending from said blade unit to said propeller assembly, a first cable clamping means mounted on said clamping member for clamping of one end of said detachable lead and a second cable clamping means mounted on said propeller assembly for clamping the other end of said detachable lead. I

2. An aircraft propeller electric deicer system as set forth in claim 1 wherein said clamping member has a lead strap clamping portion for clamping of said lead strap between said clamping portion and said blade unit and a connecting portion extending outward from said blade unit for supporting said terminals connecting the lead strap wires with the wires of said detachable lead and for supporting said first cable clamping means.

3. An aircraft propeller electric deicer system as set forth in claim 2 wherein said detachable lead has enlarged ends for preventing movement of said ends out of said first and said second cable clamping means;

4. An aircraft propeller electric deicer system as set forth in claim 3 wherein said propeller blade unit is rotatable relative to said propeller assembly to adjust the pitch of the propeller blade and the length of said detachable lead is at least as long as the maximum distance between said first and said second clamping means to accommodate changes in the pitch of the propeller and said propeller unit.

5. In an aircraft electric deicer system having a boot containing a resistance-type electric heater mounted on a propeller blade, a lead strap containing lead strap wires extending from said boot radially inward to a clamping member mounted on a propeller blade unit having pitch adjusting rotation relative to a propeller assembly wherein the improvement comprises a detachable lead strap extending from said blade unit to said propeller assembly, said detachable lead strap having flexible wires connected to said lead strap wires at said clamping member and a sleeve member around said flexible wires providing a covering for clamping at said clamping member. and at said propellerassembly.

6. An aircraft electric deicer system of claim 5 wherein said sleeve member has enlarged ends for retaining said detachable lead strap in clamped position at said clamping members and at said propeller assembly.

7. An aircraft electric deicer system of claim 6 wherein said sleeve member is of heat shrinkable material and each of said enlarged ends comprises an annular ring disposed around said wires of said detachable lead strap and extending radially outward after said sleeve has been heated and shrunk around said ring.

8. An aircraft electric deicer system of claim 5 wherein said wires of said detachable lead strap have a plurality of strands and each of said wires is encased in two layers of fabric with a layer of insulating material interposed between said two layers of fabric.

9. An aircraft electric deicer system of claim 6 wherein said sleeve member is of heat shrinkable material and each of said enlarged ends comprises an O-ring of resilient rubberlike material around said wires of said detachable lead strap and extending radially outward after said sleeve has been heated and shrunk around said ring. 

1. An aircraft propeller electric deicer system comprising a boot containing a resistance-type electric heater mounted on a propeller blade and a lead strap containing lead strap wires extending from said boot radially inward to a clamping member mounted on a propeller blade unit having pitch adjusting rotation relative to a propeller assembly, said clamping member being fastened to said propeller blade unit and having terminals for connecting the lead strap wires with wires of a detachable lead extending from said blade unit to said propeller assembly, a first cable clamping means mounted on said clamping member for clamping of one end of said detachable lead and a second cable clamping means mounted on said propeller assembly for clamping the other end of said detachable lead.
 2. An aircraft propeller electric deicer system as set forth in claim 1 wherein said clamping member has a lead strap clamping portion for clamping of said lead strap between said clamping portion and said blade unit and a connecting portion extending outward from said blade unit for supporting said terminals connecting the lead strap wires with the wires of said detachable lead and for supporting said first cable clamping means.
 3. An aircraft propeller electric deicer system as set forth in claim 2 wherein said detachable lead has enlarged ends for preventing movement of said ends out of said first and said second cable clamping means.
 4. An aircraft propeller electric deicer system as set forth in claim 3 wherein said propeller blade unit is rotatable relative to said propeller assembly to adjust the pitch of the propeller blade and the length of said detachable lead is at least as long as the maximum distance between said first and said second clamping means to accommodate changes in the pitch of the propeller and said propeller unit.
 5. In an aircraft electric deicer system having a boot containing a resistance-type electric heater mounted on a propeller blade, a lead strap containing lead strap wires extending from said boot radially inward to a clamping member mounted on a propeller blade unit having pitch adjusting rotation relative to a propeller assembly wherein the improvement comprises a detachable lead strap extending from said blade unit to said propeller assembly, said detachable lead strap having flexible wires connected to said lead strap wires at said clamping member and a sleeve member around said flexible wires providing a covering for clamping at said clamping member and at said propeller assembly.
 6. An aircraft electric deicer system of claim 5 wherein said sleeve member has enlarged ends for retaining said detachable lead strap in clamped position at said clamping members and at said propeller assembly.
 7. An aircraft electric deicer system of claim 6 wherein said sleeve member is of heat shrinkable material and each of said enlarged ends comprises an annular ring disposed around said wires of said detachable lead strap and extending radially outward after said sleeve has been heated and shrunk around said ring.
 8. An aircraft electric deicer system of claim 5 wherein said wires of said detachable lead strap have a plurality of strands and each of said wires is encased in two layers of fabric with a layer of insulating material interposed between said two layers of fabric.
 9. An aircraft electric deicer system of claim 6 wherein said sleeve member is of heat shrinkable material and each of said enlarged ends comprises an O-ring of resilient rubberlike material around said wires of said detachable lead strap and extending radially outward after said sleeve has been heated and shrunk around said ring. 